Diesel engine conversion to CNG fuel: 

                        ecological and economic dimensions

              
                            Converted to CNG  Fuel    DT-240 Diesel Engine 

                                   An abstract from the article by:

                     V.I Zakharchuk, I.S. Kozacuk, O.V. Zakharchuk  ( Ukraine)

 

Gas engine vehicles are not used as widely today as  conventional petroleum motor vehicles.  Due to this fact it is more  economically efficient to convert  existing liquid fuels engines into gas ones  on the principle of maximum unification  of  technical features of the converted engines with the basic  petroleum/diesel  fuelled ones. Previously the great majority of converted in such a way vehicles were carburetor engine ones. Or to be more precise - carburetor engine  trucks.  Yet during the last  10 years  the production of such vehicles – various types of trucks - declined while the number of diesel engine  heavy vehicles  increased.

 During these years previously low priced diesel fuel became almost  as costly as a high octane petrol. High costs of diesel fuel  makes  it economically viable  to convert   diesel fuel engines into gas engines  at least for the period of time when  there is a no serial (mass) production of gas engines trucks. Besides a converted diesel engine power loss is  noticeably less in comparison with a converted  into propan-butan gas carburetor  engine where it is no less than 8%.  A converted diesel engine has the advantage of using much higher compression  as  both diesel engine cylinders technical features  and  a very high octane  number of natural gas fuel  enable such a higher compression.

The idea of Diesel engine conversion to CNG fuel has appeared relatively recently but now there is a lot of research  on this subject in the USA, Canada, Japan, Western Europe and Russia. The results of these research works  are quite contradictory.  Besides there is no unified technological approach: only  few types of diesel engines were  test converted.

 We, the specialists of the Lutsk State Technology University, have worked out such a technology. In December 2006 at the All Ukranian Competition of Innovative Technologies we won the first prize in  one of the priority domains of this Competition. This technology enables to get quite acceptable results ( technical specifications)  for a converted engine while the conversion cost is relatively low – about 2000 US Dollars per engine.

 The conversion process includes: removal of diesel fuelling system, changing the bottom part of pistons to diminish compression ( from 16  to 12 compression ratio) and ensure  the normal  working conditions for the Otto cycle, installation of a spark  ignition system and  of serially produced gas fuelling equipments – gas fueling cylinders, high pressure and low pressure gas redactors, gas pipelines, electromagnetic valves,  etc.

This technology enables to convert  both new and  old ( after long use) diesel engines. For the latter ones the conversion is even more economically efficient  if these require repair works for cylinders, pistons and high pressure fuel pump. For the conversion of new engines it is better to order them from the manufacturer without  installation of  diesel fueling system as it makes a new engine less costly. The only basic difference  in gas and diesel engine  is the shape of the bottom of pistons.

Further the authors dwell on the real case of  D-240 diesel engine conversion for a light duty truck.  They describe, for example, the system, which prevents high rotation in a 
spark ignition gas  engine if the gas engine load rapidly diminishes.  At 1400 revolutions per minute  a converted engine yields approximately the same power as a diesel one, consuming 5,2% more of effective fuel as compared with diesel engine. The level of toxic emissions of gas engine is much lower and there is no SO2  emission. The article contains the table of  gas engine load characteristics.

The authors claim that  finance invested in such a conversion is returned within 9 to 12 months and after that period the saving effect in fuel costs is about 5000 US Dollars per annum at an average  annual covered  distance of 60 000 kilometers.

 

                     
                       

                                 Table of  DT-240 Gas engine load  and toxic

                                emissions  characteristics

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