No car owner would like to hear the statement “there is water in the engine” regarding their vehicle. What if I tell you that this can be used to increase the fuel efficiency for your car and for the betterment of environment? Anti-Detonant Injection (Water Injection Engine) is spraying of water into the incoming air or fuel-air mixture, or directly into the cylinder, for cooling the induction system from premature ignition. For the technology veterans this is an age old concept historically used during World War II era. Water in the engine was used in military aircrafts to increase the power output for a short duration during dogfights and takeoff. It has also been used in motor sport and notably in drag racing.
Currently, the automotive industry is working upon the improvements in power and fuel efficiency by injecting water, thereby enhancing the fuel economy. And in times of tight emission controls and rising petrol costs, water injection is one of the best ways of controlling detonation. Additionally, the problem of exhaust pollutants such as nitrogen oxides (NOx) and particulate matters (PM) can also be controlled through the introduction of water in the combustion chamber of diesel engine.
There are several methods of introducing water in the combustion chamber. Intake manifold water injection method (IMWIM), Diesel Oil emulsion (DOE) and Direct water injection method are few very effective ones.
Intake manifold water injection method (IMWIM)
IMWIM is widely used method for marine engine. In this method water is injected in the intake manifold during the intake stroke of the engine. There are also variations to this method in which the injector is placed near the compressor, upstream or downstream position. The popular variation is injector placement near the inlet valves. IMWIM is also popular because it is relatively easy to install and not much modification is required to integrate this system to the vehicle engine. The added benefit of uniform distribution of water in combustion chamber and ease to control the variation of water quantity also justify its popularity. The main limitation of this system is that to appreciably reduce the NOx emission, a lot of water is needed to be injected as compared to the other methods.
Diesel Oil Emulsion (DOE)
Diesel oil emulsion is the mixture of the water and diesel which are immiscible in nature hence prepared by using the emulsifiers. The DOE method is also favored because there is no need of any modification in the engine. Generally 5% to 20% by volume emulsions are used, which produces the emission control effect as par with the 60% to 65% by volume of water injection by the IMWIM. The shortcoming of the DOE method is that the variation of water quantity in fuel is not possible during operation. This factor highly restricts the performance of the method specific condition based.
Direct Water Injection Method
In this method an in-cylinder nozzle is present which injects water at the end of the compression stroke and along with fuel or the before the fuel. For which a special nozzle that injects fuel and water simultaneously or separate nozzle for the water injection can be used. This method provides more freedom as the quantity of water and the timing of injection can be controlled, which gives this method upper hand over the DOE and IMWIM. Major disadvantage of this method is the cost of modification. Additional safe guard measures must be taken so that it increases the chances of ignition delay if the device is not functioning properly.
To conclude, there are advantages and disadvantages related to each method and conditions under which they outperform the others. But each one of them is capable of providing power output increase and reduces the emission levels in diesel engine application. With strict emission regulations all over the world, anti-detonant injection technology is going to be vital for the emission control of the diesel engine and with further advancement, encouragement and marketing this technology will surely proliferate as well as present in all future cars.
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An important step in this direction has been taken by BOSCH AND BMW, when they co developed the water injection system, which was first introduced in the BMW M4 GTS showcased in 2015 Geneva Motor Show. Bosch claimed that though this system only provide upto 5% power boost but it improved the fuel efficiency by upto 13% and reduced the CO2 emissions by upto 4% in the WLTC. Bosch has expected this system to be used in mass production for wide range of cars by 2019.
Tauzia, Xavier, Alain Maiboom, and Samiur Rahman Shah. “Experimental study of inlet manifold water injection on combustion and emissions of an automotive direct injection diesel engine.” Energy 35.9 (2010): 3628-3639.
Energy and Power
p-ISSN: 2163-159X e-ISSN: 2163-1603
2015; 5(1A): 28-33
Effect of Introduction of Water into Combustion Chamber of Diesel Engines – A Review
Shyam Prasad H 1, Joseph Gonsalvis 2, Vijay V. S. 2
(Ingenious e-Brain Solutions)