With the engine completed, it was time to run some tests and find out if the HR-1 would work as planned. The engine was rolled out on its test stand and fired up. The engine did manage to run. Throughout many tests, a few minor problems were noticed and steps were taken to correct them.

Scroll entrance burned away

This is what happens when one of these engines overheats. The fuel was not burning fast enough and carried the immense heat into the scroll entrance. It was so hot it acted like a torch and melted the metal away. To fix the inlet, a grinding stone was used to remove the areas of the cast iron that had melted. The metal was then smoothed out to attempt to avoid having a hard edge that could create further hot spots.

Jet nozzle

This nozzle is the same size as the turbine exit and goes up inside sealing off at the housing. I did this because the opening of the turbine scroll is five inches and the turbine wheel is three and three quarters. The nozzles were made from five-inch pipe that I added a step on to so the size would be reduced. I thought it was stupid to let the air slow down in that five-inch pipe and then try to speed it up again out of a smaller diameter nozzle. I have the same thrust with this nozzle as with the old one, but the turbine temperature was much lower.

Extended jet nozzle

This is the jet nozzle that I am now using Even with the extreme heat the turbine is in good condition. The nozzle has been extended in length from the previous version shown above.

I have worked a year on this engine and the best thrust output that I managed was 45 pounds of thrust. This is the engine that was used on the jet kart. I tried different nozzle sizes and even used a jet nozzle that was the same diameter of the turbine. The fuel consumption is 13 gallons an hour. The problem that I have run into is the higher thrust levels caused severe overheating of the turbine. The turbine inlet temperature climbs to over 1900 degrees Fahrenheit with a turbine outlet temperature of 1700 degrees. I only kept the output high for a few seconds at a time. I have tried to lower the temps but all attempts have failed. It seems that every time it ran cooler the thrust output was considerably lower.

These tests were conducted using the same fuel pressures and nozzle sizes. All of the tests have led me to the conclusion that the combustor is too small. The air flow through the combustor is too high and the fuel is taking to long to fully burn and is entering the turbine scroll while it is still burning. I have started work on a new combustor, flame tube and inlet pipe. It will also use two smaller fuel nozzles to try to control the burn time. I do not know if this will perform any better, but I will try nonetheless. I have not totally given up on this design yet. I am reconfiguring the combustion chamber so that the air will now come in on the side closer to the top. This should swirl the air around in the combustor more and help in the combustion of the fuel. I am also going to change the fuel injector nozzles to attempt to get better atomization.

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New fuel nozzles

I purchased several water misting nozzles from Mc Master Carr. I will test them first and see if they will deliver smaller fuel droplets. If so, I think it should complete the burn by the time it reaches the secondary air holes. Testing will verify if this is the case or not.

The new nozzle installed on the combustor

Sept 28, 2005 I tested the new nozzles I received from Mc Master Carr and found that they do deliver a finer mist compared to the agricultural nozzles that I had been using. I will be finishing up the modifications and will test the engine soon.

Nozzle mounted to end cap

The new nozzles mount to the combustor end cap in the same way as the previous agricultural nozzles. The smaller tube to the left of the nozzle is the propane inlet, which serves as the pilot to ignite the diesel fuel as it is injected into the combustor through the main nozzle.

Relocated air inlet

The air inlet to the combustor was relocated to create a better air distribution throughout the entire length of the flame tube.

Combustor sealed

As the air inlet to the combustor was relocated, the original inlet hole had to be sealed. A piece of plate steel was formed to match the outer radius of the combustor and was welded in place over the old opening.

Top of flame tube

There is a small opening at the top of the flame tube to cut down on the amount of air that is getting by. The fuel is sprayed directly into the hole on the end of the flame tube.

As of Sept 30, 2005 I had finished work on the modified combustor and tried to start it. A let down to say the least. I was almost able to get it to spool up, but it would flame out. I think that there was too much frontal air getting around the nozzle. There are air holes along the side of the nozzle, and with the relocation of the air inlet it would appear that there was too much airflow that was interfering with the burn process directly after the nozzle. It was time to redesign the flame tube at the nozzle and inlet areas and retry.

With further modifications and testing completed, I reassembled the engine and was able to start it. It ran well and the temps were down. Sealing off the top of the flame tube worked well. The turbine inlet temp was 1200 degrees Fahrenheit instead of 1700 to 1900 and the turbine outlet temp was at 1000 degrees. The thrust was not quite as good as I wanted, as it was only 38 pounds at full throttle. I am using a 15 gph (gallon per hour) nozzle, but with a much finer spray. The next thing I checked for were any cold spots in the flame tube where the fuel was not burning correctly. The maximum combustor pressure reached was 32 PSI. The combustor needed to reach an internal pressure of 40 PSI to see any noticeable increase in thrust output over the previous results. It would appear that the combustor was consuming more fuel without a noticeable increase in power output.

Additional work on the engine yielded acceptable results. I was able to get the thrust back up and it was atomizing and burning the fuel well. The temperatures will still go very high on the TIT's (turbine inlet temperature) but the TOT's (turbine outlet temperature) are marginally safe. I took the engine for a drive (see the jet kart for the details). The engine did not reach the 40 PSI combustor pressure but did manage to get up to 36 PSI. I added an improved nozzle to the jet pipe and it seems to have helped.

With this stage of engine development and testing complete, the engine was grafted onto a go cart chassis. Full details of the jet kart and the build are available in the jet kart section of the site. The engine has since undergone a new development stage which is documented in the HR-1A section of the site. It is the further development of the engine with a new combustion chamber designed to achieve maximum power from the engine.

I hope that you have enjoyed reading about the initial development of the HR1 engine.

Gary Richards

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