HAM principle

HAM principle

Over 90% of NOx   formation results from combustion temperature peaks. The principle of HAM is to humidity the inlet air in order to lower these temperature peaks.

The HAM system humidifier produces saturated air. The ability of water to decrease the formation of NOx is exploited in the same way as with fuel water emulsification. but the quantity of water added is much higher and the heat for water vaporization is taken from the compressed air after the turbocharger or other engine—related heat sources.

When the water vapour is mixed with the compressed charge air, two mechanisms can be identified:

• Increase of the specific heat capacity of the mixture
• Dilution of the charge air: water vapour replaces air

The quantity of water (in g/kg dry air) which can be injected into the inlet air depends on the temperature and the pressure of the mixture.

With the HAM method a NOx reduction level of 40% is achievable without using additional heating of the intake air and a level of 65% when additional heat is introduced from the engine coolant or exhaust gases.

How HAM works

The functional principle of HAM is quite simple.

Figure illustrates the HAM Process:

1. Filtered saltwater is pumped to the catch tank to replace evaporated and purged loop water.

2. The HAM system itself cycles water in a loop between the catch tank and the Humidification tower(“HAM vessel”)

3. A heat exchanger between the catch tank and the HAM vessel heats the saltwater using an on-engine heat source.

4. Three injection stages spray the heated saltwater into the charge air.

5. At the same time the compressed charge air from the exhaust turbocharger bypasses the charge air cooler and is piped into the HAM vessel air inlet. Flowing through the HAM vessel, the charge air absorbs the water. Due to the high loop capacity of the water all particles (incl. salt) fall back into the catch tank and, over a certain salinity level, are purged. Thus no salt from the saltwater can enter the engine.

6. To avoid tiny droplets reaching the combustion chamber, the humidified charge air passes through a high-perforrnance mist catcher at the end of the humidification tower.

7. This humidification leads to saturated charge air which is fed into the engine.

Advantage of HAM

1. Low maintenance and operation costs
2. NOx reduction up to 70%
3. Safe and ecological process
4. Improved performance at part load operation, dependent on available heat
5. ‘Lighter’ system.
6. No fuel quality limitation :The engine can run on high sulphur fuel oil (HSFO)
7. No additional reducing agent (uses sea water only), water decalcification agent necessary
8. Exhaust gas temperatures and valve temperatures are lower, leading to a decrease in thermal loading.
9. The system is intrinsically self-controlled without any need of a load-related control loop. The system is stable and responsive.
10. Stable: No abrupt changes in engine operating parameters if water circulation is shut—off.