the concept discussed herein is directed to an atomizer design that reduces the chance of atomizer plugging , whether the liquid being sprayed is fuel , urea - water mixtures , or some other liquid or liquid mixture that is subject to thermal degradation . this concept may be implemented as an improvement to an existing , commercially available atomizer . the concept reduces or eliminates the probability of thermal degradation of the liquid being sprayed , while extending the flow range of the atomizer . fig1 illustrates an example of the type of atomizer with which the invention may be used . this atomizer 10 is the commercially available pressure - atomized variflo ™ bypass nozzle , available from delavan spray technologies . atomizer 10 comprises a nozzle 10 a screwed into an adapter 10 b . in accordance with the bypass design of atomizer 10 , with constant supply pressure at inlet 10 c and with bypass channel 14 closed , the nozzle 10 a operates as a simplex nozzle with the liquid being delivered via spray channel 13 and sprayed out from orifice 11 a . with the bypass channel 14 open , part of the liquid is allowed to return to a source reservoir ( not shown ), with the result being reduced discharge flow . the atomization principle of atomizer 10 is based on swirling the liquid in a swirl chamber just upstream of an orifice disk 11 . as a result of the swirling , a thin sheet of liquid flows along the outer edges of the orifice disk 11 . the liquid is then atomized as it leaves the orifice 11 a . the swirling flow is created by narrow slots cut at an angle in the distributor 12 . as discussed in the background , a limitation to any atomizer for applications in a hot environment is that when the spray is turned off , that is , when flow is stopped in the atomizer , the liquid remains in the tip and may be subject to thermal degradation . if the atomizer is then turned back on , the atomizer may then be clogged or if not clogged , the atomized liquid may be degraded . in an atomizer such as the example of fig1 , the problem is exacerbated by the fact that the slots in the distributor 12 are quite small and easy to plug . fig2 illustrates the concept proposed herein . the modified atomizer 20 is cooled with the same fluid that is to be sprayed from the atomizer . for cooling , fluid from reservoir 25 is directed to a cooling channel 21 , which leads to a annular channel 21 a machined into adapter 10 b in the region where the nozzle 10 a screws into the adapter 10 b . the fluid in the annular channel 21 a cools the adapter in the area near the orifice . as indicated by the dotted lines , if desired , after a heat exchange occurs , the liquid may be directed out of the atomizer via the bypass channel 24 . to this end , the annular channel can be made to be in liquid communication with the bypass channel . the circulated liquid flows back into the liquid supply reservoir 25 . the atomizer &# 39 ; s normal valve , used to turn off and on liquid flow to the atomizer , and located upstream from the atomizer , is replaced with a 3 - way valve 22 which directs flow from a supply pump 26 to either the atomizer spray path 23 , in the normal way , or to the cooling channel 21 when the spray is turned off . thus , depending on the setting of valve 22 , the liquid flows in a spray path ” 23 when the atomizer is on ( spraying ), and a cooling path 21 when the atomizer is off ( not spraying ). when the spray is stopped ( off ) and the liquid is circulating within nozzle 10 a via the cooling channel 21 , the atomizer remains relatively cool , below the liquid thermal decomposition point , by its thermal contact with the adapter 10 b . the standard liquid pump 26 that supplies pressure to the atomizer may be used to cool the atomizer even when the atomizer is not spraying liquid . in this way , a standard atomizer nozzle 10 a can be used and replaced as necessary . if the atomizer already has a bypass channel 24 , the only modification is to the adapter 10 b that holds the nozzle 10 a . in practice , the cooling channel 21 could be bored into the adapter body , or it can be external to the adapter . if the atomizer does not already have a bypass channel for permitting liquid to exit the circulation chamber , the atomizer may be modified to have an exit channel . if a high - pressure boost pump ( not shown ) is used to increase the pressure from a supply pump to improve atomization quality , the 3 - way valve 22 may be placed upstream of the high - pressure pump , as even low pressure is sufficient for cooling the atomizer . a check mechanism may be necessary as part of bypass valve 27 to avoid liquid flow backward through the bypass line if the drain is arranged as shown in fig2 . some existing fuel injectors provide fuel flow through the injectors even when they are not spraying fuel . however , in these injectors , the purpose of the fuel flow is not to cool the injector , but rather , to provide fuel in a convenient location to be injected when required . in those injectors , an expensive solenoid control valve must be built into the fuel injector , greatly increasing the cost . in general , the modification discussed above is to an atomizer having a housing surrounding the nozzle . in the example of fig1 and 2 , the housing is a removable adapter 10 b . the housing has an annular channel 21 a for containing the liquid delivered from the reservoir via the circulation channel . the liquid may enter ( or remain in ) this annular region even when the spray is turned off and is pressurized by the same pressure used for providing the spray . fig3 illustrates an alternative embodiment of the invention . a circulation cylinder 31 has been added in the region of the atomizer nozzle . cylinder 31 permits liquid that is normally sprayed through the atomizer ( when the atomizer is “ on ”) to flow through the cylinder 31 on one side of the nozzle and to exit on the other side . the flow of liquid inside cylinder 31 can take many forms . as another example , the liquid can flow around the nozzle . cylinder 31 may be easily attached to an existing housing , such as adapter 10 b . in fact , for purposes of generality , both the embodiment of fig2 and the embodiment of fig3 could be described as having a housing ( adapter 10 b or cylinder 31 ) having an annular bore around the nozzle 10 a . as illustrated in fig3 , the discharged liquid can flow out through an existing bypass line 14 . alternatively , for atomizers not already having a bypass line , an exit line can be provided . other elements of fig3 are similar to those of like numbering in fig2 . for the embodiments of fig2 and 3 , the modifications described herein allow the atomizer to be used for intermittent operation in a hot environment . without the modification , the atomizer would suffer from thermal degradation of the liquid in the atomizer and eventual atomizer plugging . the thermal degradation point for fuels like diesel fuel is above 200 ° c ., so maintaining the atomizer temperature lower than that value should prevent degradation . for urea - water mixtures , the temperature is lower , probably less than 70 ° c .