As we all know that DRDO is currently working on a range of diesel engines, the question arises why in the age of electrification and gas turbines, DRDO is still trying to develop conventional diesel engines and plan to use them in the next generation tanks.
Before diving deep into the discussion, let’s discuss a bit about the working principles of both the engines. Conventional ICE or Internal Combustion engines work on the 4- stroke principle which include intake, compression and power and exhaust strokes.
Intake: Mixture of fuel and air and in case of a direct injection engine, only air enters the combustion chamber.
Compression: In this stroke, the air and fuel mixture either pre mixed or mixed within the cylinder is compressed by the piston towards top dead centre.
Power Stroke: In this stroke, the explosion produced at the end of previous stroke is used to move the piston down in turn rotating the crank shaft which transfers the power to the wheel via clutch, gearbox and shaft.
Exhaust Stroke: In this stroke, the burnt gases will be expelled out of the engine and the cycle repeats itself.
Gas turbine engine:
A gas turbine engine consists of a series of compressors and turbines along with combustion chambers to burn the fuel and generate thrust. The process starts with multiple stages of compressors (mostly two to three stages) will compress the air entering them and this compressed air is then sent into the combustion chambers where fuel is injected and the burnt gases are then sent to the turbines which in turn rotate compressors which are connected to the turbine via a common shaft. When these gases are expelled from turbine, it will rotate the shaft.
As we have discussed about how both these engines work, we will look at why one is better over the other. Before going into this, we will discuss about the prospects of a 2- stroke diesel engines as asked by some people. 2-stroke engines theoretically should develop twice the power of an equivalent 4-stroke engine as there are two power strokes for one cycle of a 4-stroke engine. But 2-stroke engine also generate more vibrations, more emissions than 2-stroke engines so these engines are out of the picture.
There are a couple of reasons why DRDO is developing new ICE engines in the age of electrification and gas turbine power plants.
- Fuel commonality
As we all know ICE engines especially in MBTs work on diesel, this fuel also run armed force’s other vehicles such as BMPs, heavy trucks and other vehicles. This commonality in fuel will bring an advantage to armed forces as only one type of fuel needs to be carried. This is also one of the reasons why army selected Tata safari as their new vehicle which runs on diesel as their older Maruti Gypsys used to run on petrol and petrol was carried separately. Though army ordered new Gypsys for other reasons, commonality brings down the costs of logistics.
- Compact packing
ICE engines are compact powerplants when compared to its gas turbine counterparts. Even if we make a guess, the new 1500 bhp engine that is being developed by DRDO will occupy a volume of 6-7 m^3 with all of the subsystems such as turbo charger, intercooler, air filter ad cooling systems included. A gas turbine engine of similar capability will require more volume than the ICE counterpart.
- Development and operation costs
Its common knowledge that developing and running gas turbine engines is more costly compared to regular ICE engines as the turbines and compressor blades will require precision engineering to design and develop. Also the metallurgy of gas turbine systems is more complicated and advanced than the IC engines. Accordingly even the operating costs of gas turbine engine are quite high.
- Manufacturing costs
A regular IC engine costs much less to manufacture than a gas turbine engine as India has achieved a lot of experience in manufacturing IC engines. SO finding manufacturing partners for competitive prices in not a big deal as there are thousands of suppliers around the country. If automotive companies such as Mahindra and Tata are involved in making and assembling the engine, the expertise they have in manufacturing will help CVRDE achieve the required quality standards set by Indian armed forces. Moreover, these IC engines ca be used to update the older tanks and other vehicles and keep them running.
- Serviceability and reparability
The serviceability and reparability are the parts where IC engines have the biggest advantage over the gas turbine engines. As the gas turbines involve complicated parts, the service staff needs additional and rigorous training than they receive for servicing regular IC engines. This increases the training costs and can affect the readiness of armed forces. Moreover for a matter of fact, a mechanic can repair an IC engine with minimum knowledge or at least diagnose the issue in times of need as IC engines have a wide spread use around the country.
Overall if we consider all these factors, it seems like IC engines as of now are a better and affordable choice for our current and future MBT programs as they have the versatility that a gas turbine engine doesn’t offer in terms of costs, maintenance and manufacturing. This also helps to streamline the logistics of the armed forces as sae engines can be used in multiple platforms.