RECENTS DEVELOPMENTS IN IC ENGINE DESIGN
The world is rapidly moving towards hybrid and electric vehicles. So, it’s natural to think that all the automobile manufacturers are developing only hybrids and EVs, neglecting the conventional IC engine.
Now you might be wondering that in the age where everyone is doing research and writing blogs on EVs, why would someone write a blog on ICEs? This is because of the passion, enthusiasm and love for the ICEs. Also, even while developing a hybrid, ICs are inevitable. “People tend to forget that even though it might be hybrid or plug-in hybrid, these vehicles all still need an internal combustion engine,” said Paul Seredynski, manager, global powertrain technology communications for Ford Motor Co. “It’s one of the main reasons why Ford is so bullish and why the research continues to focus so heavily on internal combustion.”
According to the popular CarAndDriver Magazine, “EVs are the future, but vehicles with internal-combustion engines are not going to disappear any time soon”
Right from the time of their invention in the 1800s, IC engines are undergoing a lot of development. They are being developed to take us from one place to another faster and in a more efficient way.
Nowadays, the main objectives are the minimization of fuel consumption/CO2 emissions and the mitigation of exhaust pollutants. To this aim, various alternative combustion techniques have been developed, or are under development (e.g., direct injection SI engines, HCCI operation etc.); various internal and after-treatment exhaust measures are also being examined.
One particular aspect of (automotive) engines is dynamic operation, which is responsible for the largest number of emitted pollutants. Acknowledging this fact, the certification (both driving and engine) cycles for all kinds of vehicles are highly transient.
Another significant aspect of modern engines is their supercharging, realized mainly through various turbocharging configurations. Today, turbocharging an I.C. engine is a well-established means for achieving lower CO2 emission targets, as is also the use of hybrid electric powertrains.
In parallel, the use of alternative fuels and biofuels has boomed in the last few decades, as these have proven to be promising in limiting carbonaceous pollutants emissions, while, at the same time, providing a positive CO2 balance.
The need for fuel efficiency took a giant leap forward in the mid-1970s during the first and second Arab Oil Embargoes, which saw a sharp increase in gasoline prices due to the price of oil increasing 400 percent from $3 to $12 a barrel. Since then, the Detroit Three have worked to improve on an engine that continues to see improvements in fuel economy during the ever-evolving race to go green.
Ever since, IC engines are being developed to run in a more efficient manner.
In the US, one of the major rivalries between automobile manufacturers is of Ford and Chevrolet.
The most recent evolution of the research done by Ford, the OEM’s 2.7L EcoBoost engine, will see its first application in the next-generation aluminum-bodied Ford F-150. It will have a better miles per gallon efficiency because of the new engine. It’ll also be 700-pound lighter which comes with switching to aluminum. This is a strategy that Seredynski related to meeting the fuel-efficiency needs of the customer in a completely different way.
The combination of different vehicle technologies is a strategy most OEMs are leaning toward when it comes to improving mpg. At General Motors, engineers are integrating vehicle and powertrain strategies together to optimize and minimize unnecessary parts, according to Roger Clark, senior manager, energy center for GM.
“Great examples of technologies that improve vehicle efficiency include added transmission gears (e.g., 6-speed versus 4-speed) lowering engine operation speed, enabling lower numerical axle ratios, and, in many cases, increasing performance and capability,” Clark said. He added variable cam phasing, direct fuel injection, reducing engine accessory loading, electric power steering, improved vehicle aerodynamics, increased cooling airflow sealing, and reduced tire rolling resistance to the list.
GM is also increasing its attention to what it calls “opportunity-type” controls. For example, using start/stop technology to stop the engine at idle and seamlessly restart it when the brake is released, and advanced battery charging that helps to charge the battery from regenerated vehicle kinetic energy.
For Chris Cowland, director, advance and SRT powertrain engineering at Chrysler, optimization of existing combustion, thermodynamic, and gasoline exchange technologies, as well as improving mechanical processes, will increase the overall efficiency of the ICE.
“From a combustion perspective, we are adding technologies that allow us to operate as close to the stoichiometric air/fuel ratio as possible without the need for fuel enrichment to manage exhaust temperatures,” Cowland said. “An example of such technology is the integrated exhaust manifolds used on the Pentastar engine.”
The Chrysler Pentastar Engine family is a series of aluminum (die-cast cylinder block) dual overhead cam 24-valve gasoline V6 engines, which were introduced for the 2011 Chrysler, Dodge and Jeep Vehicles.
The variable displacement oil pumps, according to Cowland, also enable the oil output of the pump to be tailored to the demand of the engine rather than pressurizing and then recirculating excess fluid.
While Porsche is fully committed to electrification, and expects 80 per cent of it’s lineup to be electrified by 2030, it is also committed to further sustainable synthetic fuels to power IC engine cars well into the future. And it has good reasons to. According to some estimates, 70 per cent of all Porsches ever made are still on the road!
However, the biggest reason is that Porsche’s 911 line, with their engines in the rear of the Car, aren’t suited to full electrification. While some hybridization is possible, Porsche is instead looking to further develop its synthetic fuels, which it claims is carbon neutral, and has a large carbon footprint as the production and use of an EV
eFuels are essentially complex hydrocarbons that have been created by man, rather than the lengthy natural and man-made process it takes to create fossil fuels. Water is separated into hydrogen and oxygen using wind-generated electricity and then CO2 filtered from the air is combined with ‘green hydrogen’ to form methanol. It’s then turned into useable fuel by ExxonMobil-licensed Methanol to Gasoline (MTG) technology.
The fuel is sourced from the Haru One Pilot Plant in Chile that Porsche announced late last year. The plant uses wind-generated electricity to split water into hydrogen and oxygen. The hydrogen is then combined with atmospheric carbon dioxide to produce methanol, which in turn forms the basis for synthetic fuel.
The eFuels that Porsche is testing use CO2 and hydrogen ingredients and are made using renewable energy, which significantly lowers the greenhouse gas emissions compared to petroleum-based fuels.
Porsche is far from first to dip into synthetic-fuel research. Audi, Bosch, and McLaren have all been talking about and working on the technology for years.
In the race for greener mobility, nearly every automaker is now focused on electric vehicles. But buying an EV doesn’t change the fact that the vast majority of cars being sold today are powered by gasoline, and they’re going to remain on the road for a long time. As a way to make driving existing vehicles more sustainable, Porsche has been working on synthetic fuels it calls eFuels that the company says can make an internal-combustion engine as clean as an EV.
Porsche’s eFuels are made out of CO2 and hydrogen and are produced using renewable energy. The final result is a liquid that an engine will burn the same as if it was gasoline made from crude oil, but an eFuel can be produced in a climate-neutral manner, at least in theory. Speaking at the recent launch of the new 911 GT3, Porsche vice president of Motorsport and GT cars Frank Walliser said the company will have its first small test batch, just 130,000 liters, or 34,340 gallons of eFuel ready by 2022.
“Synthetic fuel is cleaner and there is no byproduct ,and when we start full production we expect a CO2 reduction of 85 percent,” Walliser told the U.K. publication Evo. “From a ‘well to wheel’ perspective, and you have to consider the well-to-wheel impact of all vehicles, this will be the same level of CO2 produced in the manufacture and use of an electric vehicle.”
Some of the recent trends we see in our modern-day ICs are:
- Start- Stop Technology: This method is used to stop the vehicle when it is idle for a long period of time. i.e., during traffic. This helps in reducing fuel consumption. Now, to start the vehicle, it is enough to hold the clutch. This method also reduces emissions.
2. Catalytic Converters: Today, due to the stringent emission norms, after treatment devices are necessary to bring down the emissions in an IC engine. Catalytic converters are one of the devices which reduces the emissions from IC engines, thereby making them to comply with the emission standards.
3. Downsized boosting: In this method, the engine size is reduced. It is downsized according to the norms and regulations. Downsizing the engine helps reduce emissions. One of the most popular MPVs in India is the Toyota Innova. In the previous generation, the top end featured a 2.8L diesel engine. But in the updated version, the top end is available with a 2.7L engine. Same is the case with Ford Endeavour. The top end came with a 3.2L engine, while the updated model has only a 2L option
4. Cylinder pressure sensing: The pressure inside the cylinders is monitored and is maintained at required conditions. Accordingly, the turbocharger is made to function
5. Dilute combustion: Nowadays, the fuel is diluted by passing more air than usual in it. This makes the fuel lean and reduces emission.
At the rear ends of our cars, we see some badges likes TDI, VVT, etc. What do they mean? They tell us the type of engine our vehicle has. These are the modern ICEs which have evolved through time and have been developed. Some of them are:
- Turbocharger (TDI- Turbocharged Direct Injection): These are nothing but turbines which are operated by engine exhaust gases to produce power for a compressor which is in turn used to increase the mass flow rate of air, which is sucked inside during the intake stroke. This method, increases the power and performance of an IC engine.
- Gasoline Direct Injection (GDI) : This method is often used in Gasoline engines. As the name indicates, it involves the direct injection of Gasoline into the combustion chamber of an engine by means of electrically controlled actuators and sensors. This method helps in metering the quantity of the fuel injected, based on our requirements thereby reducing fuel consumption.
- Variable Valve Timing (VVT): This method involves the electronic control of valves, thereby adjusting the valve opening and closing mechanism based on our needs. This technology also improves fuel efficiency and performance.
- Common Rail Direct Injection (Crdi): This method is often used in Diesel engines to control and maintain the effective usage of fuel under different conditions. It consists of a common rail, where the fuel accumulates and then supplied to the cylinders through high pressure injectors.
Over the past few years, we have been witnessed some new trends in ICEs
Cylinder deactivation
· Cylinder deactivation is one of the technologies that improve fuel economy. Its objective is to reduce engine pumping losses under certain vehicle operating conditions
· It is the method of deactivating the cylinders as per power requirement of engine to achieve better fuel efficiency. It also helps in emission control.
· It works because only a small fraction of an engine’s peak horsepower is needed to maintain cruising speed.
Advantages
• Lean combustion: It increases 15% increase in fuel efficiency over a conventional SI engine
• Cleaner combustion: It produces cleaner combustions and lower emissions (NOx) than conventional SI engines
• Compatibility: They’re compatible with gasoline as well as E85 (ethanol) fuel.
• Easy fuel burning: Fuel is burned quicker and at low temperatures, reducing heat energy loss as compared to the conventional SI engine
• Throttle less induction: It eliminates frictional pumping losses incurred in traditional (throttle body) SI engines.
Disadvantages:
• Engine balancing- Deactivating cylinders can cause change in engine balancing which can lead to very violent vibration and increased noise levels.
• Increased cost of manufacturing- the cost of the additional parts like electronic control module and the complexity in the design and lifter pin mechanism will increase the cost of manufacturing
• Overall increase in weight- Due to the presence of additional components like hydraulic lines used in hydraulic sub system, lifter locking mechanism, and solenoid valves etc.
• Complexity of system makes maintenance difficult. — Complex lifter locking mechanism and solenoid valves are difficult to maintain.
Direct fuel injection
In this method, fuel is directly injected into the cylinders and is not mixed with air in the inlet manifold or inlet ports before drawing into the cylinders.
Types of DIs:
• MPFI Engine (Multi Point Fuel Injection system): In this system each cylinder has number of injectors to supply/spray fuel into the cylinders .
• CRDI Engine (Common Rail Direct injection system): In this system, all the injectors are supplied by a common fuel supply line or a manifold called the common rail.
Advantages
- Due to multiple injections, uniform A/F mixture supplied to cylinder, thus difference in power developed in each cylinder is minimum. Noise and Vibration from the engine is less.
- Since the engine is controlled by ECU, accurate A/F mixture supplied resulting in complete combustion leading to effective utilization of fuel supplied and hence low emission level.
Disadvantages of direct fuel injection
- The primary disadvantages of direct injection engines are complexity and cost.
- Direct injection systems are more expensive to build because their components must be more rugged — they handle fuel at significantly higher pressures than indirect injection systems and the injectors themselves must be able to withstand the heat and pressure of combustion inside the cylinder.
Variable Valve Timing and lift
Here, the principle is to use a two-position advance or retard of either an engine’s intake or exhaust camshaft to better match the engine’s operating conditions.
Two main factors that determine an IC engine performance are
• The point at which valves open.
• The duration of the valves being open.
Types of Variable Valve Timing System
VTEC Engine (Variable Valve-Timing and Lift Electronic Control) VTEC works by varying valve timing and lift to compensate for the time delay and out-of-phase arrival of the air-fuel charge at the intake valve. Shifts valve between two separate sets of cam lobes — one for high-speed operation and one for low.
Advantages
- Low fuel consumption appreciable increase in power
- Lower tail pipe emission.
- Valvetronic system, optimize engine power and efficiency.
- Reduces pumping losses
Disadvantages
- Has a complex design to manufacture
- Is expensive
- High wear and tear occur
- Very difficult to maintain
Turbocharger
• A turbocharger is a turbine-driven forced induction device that increases an internal combustion engine’s efficiency and power output by forcing extra air into the combustion chamber:
• This improvement over a naturally aspirated engine’s output results because the turbine can force more air, and proportionately more fuel, into the combustion chamber than atmospheric pressure alone.
• Turbochargers are commonly used on truck. car, train. aircraft, and construction equipment engines. They are most often used with Otto cycle and Diesel cycle internal combustion engines.
Working principle of Turbocharger
- A turbocharger is a small radial fan pump driven by the energy of the exhaust gases of an engine.
- A turbocharger consists of a turbine and a compressor on a shared shaft.
- The turbine converts exhaust to rotational force, which is in turn used to drive the compressor.
- The compressor draws in ambient air and pumps it in to the intake manifold at increased pressure, resulting in a greater mass of air entering the cylinders on each in take stroke.
Advantages
- The more increase the pressure of the intake air above the local atmospheric pressure (boost), the more power the engine produces.
- Engines burn air and fuel at an ideal ratio of about 14.7:1, which means that if you bum more air, you must also bum more fuel.
- This is particularly useful at high altitudes: thinner air has less oxygen, reducing power by around 3% per 1,000 feet above sea level, but a turbocharger can compensate for that loss, pressurizing the intake charge to something close to sea level pressure.
Disadvantages
- Cost and complexity
- Detonation
- Large space requirement
- Turbo lag
Homogeneous Charge Compression Ignition (HCCI)
A mixture of fuel and air ignites when the concentration and temperature of reactants is sufficiently high. The concentration and/or temperature can be increased in several different ways:
· Increasing compression ratio
· Pre-heating of induction gases
· Forced induction
· Retained or re-inducted exhaust gases
Once ignited, combustion occurs very quickly. When auto-ignition occurs too early or with too much chemical energy, combustion is too fast and high in-cylinder pressures can destroy an engine. For this reason, HCCI is typically operated at lean overall fuel mixtures.
Advantages
· Since HCCI engines are fuel-lean, they can operate at diesel-like compression ratios (>15), thus achieving 30% higher efficiencies than conventional SI gasoline engines
· Homogeneous mixing of fuel and air leads to cleaner combustion and lower emissions. Because peak temperatures are significantly lower than in typical SI engines, NOx levels are almost negligible. Additionally, the technique does not produce soot
· HCCI engines can operate on gasoline, diesel fuel, and most alternative fuels
· HCCI avoids throttle losses, which further improves efficiency.
Disadvantages
· Achieving cold start capability.
· High heat release and pressure rise rates contribute to engine wear.
· Autoignition is difficult to control, unlike the ignition event in SI and CI engines, which are controlled by spark plugs and in-cylinder fuel injectors, respectively
· HCCI engines have a small torque range, constrained at low loads by lean flammability limits and high loads by in-cylinder pressure restrictions
· Carbon monoxide (CO) and hydrocarbon (HC) pre-catalyst emissions are higher than a typical spark ignition engine, caused by incomplete oxidation (due to the rapid combustion event and low in-cylinder temperatures) and trapped crevice gases, respectively.
Conclusion
Internal combustion engines are among the most important engineering applications. The theory of application either depends on Diesel or Otto cycles. They are categorized either according to the operating cycle, or due to the mechanism of working.
In spite of the world marching towards hybridization and electrification, ICs are still sought being developed to make the vehicle faster and more efficient.
We would like to thank our sources, Car and Driver Magazine, Evo UK, Overdrive and Automotive Fleet.
By: Harsh Bhutani, Abhishek Chavan, Atharva Chitnis, Dharmesh Chowdhary, Arjun Desai
harsh.bhutani18@vit.edu, abhishek.schavan18@vit.edu, atharva.chitnis18@vit.edu, dharmesh.chowdhary18@vit.edu, arjun.desai18@vit.edu
